Technical Field
Embodiments described herein are related to electrostatic discharge (ESD) protection in integrated circuits.
Description of the Related Art
The transistors and other circuits fabricated in semiconductor substrates are continually being reduced in size as semiconductor fabrication technology advances. Such circuits are also increasingly susceptible to damage from ESD events, thus increasing the importance of the ESD protection implemented in integrated circuits.
Typical ESD protection circuits include diodes that are connected between integrated circuit pin connections and power/ground connections. The diodes are designed to turn on if an ESD event occurs, rapidly discharging the ESD event to avoid damage to the functional circuits (e.g. driver/receiver transistors) that are coupled to the connections. Fin field effect transistor (FinFET) technology further compounds the problem of providing effective ESD protection, because significant silicon volume is lost and thus forming efficient P-N junctions is a challenge. The resistance of the ESD diodes when turned “on” in response to an ESD event is often higher as a result, which reduces the effectiveness of the diodes in responding to ESD events.
One type of diode that can be used in FinFET technology is a “gated diode” or “poly bound” diode. This type of diode is used within a silicon region in which each polysilicon gate defines a boundary between N+ and P+ diffusions. Such diodes present a high capacitive load and high wiring resistance to the narrow pitch of the gates. Another type of diode is used if N+ and P+ diffusions are separated by an insulator such as silicon trench isolation (STI). These diodes are sometimes referred to as STI bound diodes, and typically have lower capacitance and wiring resistance than gated diodes.